diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index 479c5e5..3c4a722 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -63,8 +63,27 @@ jobs:
       - name: Install Linux dependencies
         if: runner.os == 'Linux'
         run: |
-          sudo apt-get update
-          sudo apt-get install -y \
+          # Hosted Ubuntu images can expose an unreachable Azure mirror in
+          # their apt sources while the public Ubuntu archive is reachable.
+          # Keep release jobs bounded and use the same source normalization as
+          # the native CI path so a runner-local mirror cannot hang packaging.
+          sudo find /etc/apt -type f \
+            -exec sed -i \
+              -e 's#http://azure\.archive\.ubuntu\.com#https://archive.ubuntu.com#g' \
+              -e 's#https://azure\.archive\.ubuntu\.com#https://archive.ubuntu.com#g' \
+              {} +
+          sudo env DEBIAN_FRONTEND=noninteractive timeout --foreground --signal=TERM --kill-after=30s 10m apt-get \
+            -o Acquire::Retries=3 \
+            -o Acquire::http::Timeout=30 \
+            -o Acquire::https::Timeout=30 \
+            -o DPkg::Lock::Timeout=60 \
+            update
+          sudo env DEBIAN_FRONTEND=noninteractive timeout --foreground --signal=TERM --kill-after=30s 10m apt-get \
+            -o Acquire::Retries=3 \
+            -o Acquire::http::Timeout=30 \
+            -o Acquire::https::Timeout=30 \
+            -o DPkg::Lock::Timeout=60 \
+            install -y \
             libwebkit2gtk-4.1-dev \
             libappindicator3-dev \
             librsvg2-dev \
diff --git a/scripts/engine-download.js b/scripts/engine-download.js
index 975953c..accdfe5 100644
--- a/scripts/engine-download.js
+++ b/scripts/engine-download.js
@@ -45,6 +45,40 @@ function createDownloadTimeout(idleTimeoutMs) {
   return { signal: controller.signal, refresh, dispose };
 }
 
+function abortReason(signal) {
+  if (signal?.reason instanceof Error) return signal.reason;
+  return new Error('Engine archive download aborted');
+}
+
+function throwIfAborted(signal) {
+  if (signal?.aborted) throw abortReason(signal);
+}
+
+function combineAbortSignals(signals) {
+  const activeSignals = signals.filter(Boolean);
+  const controller = new AbortController();
+  const listeners = [];
+  const abort = signal => {
+    if (!controller.signal.aborted) controller.abort(abortReason(signal));
+  };
+
+  for (const signal of activeSignals) {
+    const listener = () => abort(signal);
+    listeners.push([signal, listener]);
+    if (signal.aborted) abort(signal);
+    else signal.addEventListener('abort', listener, { once: true });
+  }
+
+  return {
+    signal: controller.signal,
+    dispose() {
+      for (const [signal, listener] of listeners) {
+        signal.removeEventListener('abort', listener);
+      }
+    },
+  };
+}
+
 function archiveSize(archive) {
   try {
     return fs.statSync(archive).size;
@@ -60,8 +94,26 @@ function checksumMismatchError(name, expected, actual) {
   return error;
 }
 
-function sleep(milliseconds) {
-  return new Promise(resolve => setTimeout(resolve, milliseconds));
+function sleep(milliseconds, signal) {
+  if (!signal) return new Promise(resolve => setTimeout(resolve, milliseconds));
+  return new Promise((resolve, reject) => {
+    let timer;
+    const cleanup = () => {
+      clearTimeout(timer);
+      signal.removeEventListener('abort', onAbort);
+    };
+    const finish = () => {
+      cleanup();
+      resolve();
+    };
+    const onAbort = () => {
+      cleanup();
+      reject(abortReason(signal));
+    };
+    timer = setTimeout(finish, milliseconds);
+    signal.addEventListener('abort', onAbort, { once: true });
+    if (signal.aborted) onAbort();
+  });
 }
 
 async function resetArchive(archive) {
@@ -92,20 +144,23 @@ export async function downloadEngineArchive({
   attempts = DEFAULT_ATTEMPTS,
   idleTimeoutMs = DEFAULT_IDLE_TIMEOUT_MS,
   retryDelaysMs = DEFAULT_RETRY_DELAYS_MS,
+  signal,
 }) {
   let lastError;
 
   for (let attempt = 1; attempt <= attempts; attempt += 1) {
+    throwIfAborted(signal);
     const partialSize = archiveSize(archive);
     if (partialSize > 0 && sha256(archive) === expectedSha256) return archive;
     const downloadTimeout = createDownloadTimeout(idleTimeoutMs);
+    const requestSignal = combineAbortSignals([signal, downloadTimeout.signal]);
     let resetForRetry = false;
 
     try {
       const response = await fetch(url, {
         headers: partialSize > 0 ? { Range: `bytes=${partialSize}-` } : undefined,
         redirect: 'follow',
-        signal: downloadTimeout.signal,
+        signal: requestSignal.signal,
       });
 
       if (response.status === 416 && partialSize > 0) {
@@ -143,9 +198,10 @@ export async function downloadEngineArchive({
           },
         }),
         fs.createWriteStream(archive, { flags: append ? 'a' : 'w' }),
-        { signal: downloadTimeout.signal },
+        { signal: requestSignal.signal },
       );
 
+      throwIfAborted(signal);
       const finalSize = archiveSize(archive);
       const expectedFinalSize = contentRange?.total
         ?? (expectedResponseLength === undefined
@@ -163,6 +219,7 @@ export async function downloadEngineArchive({
       resetForRetry = true;
       throw checksumMismatchError(name, expectedSha256, actual);
     } catch (error) {
+      if (signal?.aborted) throw abortReason(signal);
       lastError = error;
       if (resetForRetry || error?.code === 'ARCHIVE_CHECKSUM_MISMATCH') {
         await resetArchive(archive);
@@ -175,8 +232,9 @@ export async function downloadEngineArchive({
           { cause: error },
         );
       }
-      await new Promise(resolve => setTimeout(resolve, retryDelaysMs[attempt - 1] ?? 0));
+      await sleep(retryDelaysMs[attempt - 1] ?? 0, signal);
     } finally {
+      requestSignal.dispose();
       downloadTimeout.dispose();
     }
   }
diff --git a/scripts/engine-download.node-test.js b/scripts/engine-download.node-test.js
index da02092..6bc77f4 100644
--- a/scripts/engine-download.node-test.js
+++ b/scripts/engine-download.node-test.js
@@ -180,3 +180,48 @@ test('restarts from zero after an unsatisfiable retained range', async () => {
     fs.rmSync(directory, { recursive: true, force: true });
   }
 });
+
+test('propagates external cancellation without retrying an in-flight archive', async () => {
+  const { directory, archive } = makeArchivePath();
+  const abortController = new AbortController();
+  let calls = 0;
+
+  try {
+    await withMockFetch(async (_url, options) => {
+      calls += 1;
+      assert.equal(options.signal.aborted, false);
+      setTimeout(() => {
+        abortController.abort(new Error('provisioning interrupted'));
+      }, 10);
+      return new Response(new ReadableStream({
+        start(controller) {
+          controller.enqueue(Buffer.from('partial archive bytes'));
+        },
+      }), {
+        status: 200,
+        headers: { 'Content-Length': '100' },
+      });
+    }, async () => {
+      await assert.rejects(
+        downloadEngineArchive({
+          name: 'test',
+          url: 'https://example.test/engine.zip',
+          archive,
+          expectedSha256: digest(Buffer.from('never completed')),
+          attempts: 3,
+          retryDelaysMs: [500, 500],
+          signal: abortController.signal,
+        }),
+        error => {
+          assert.match(error.message, /provisioning interrupted/);
+          return true;
+        },
+      );
+    });
+
+    assert.equal(calls, 1);
+    assert.ok(fs.statSync(archive).size > 0);
+  } finally {
+    fs.rmSync(directory, { recursive: true, force: true });
+  }
+});
diff --git a/scripts/engine-payload-promotion.js b/scripts/engine-payload-promotion.js
index ce87263..60892a8 100644
--- a/scripts/engine-payload-promotion.js
+++ b/scripts/engine-payload-promotion.js
@@ -50,6 +50,33 @@ async function removeOrphanedPreviousPayloads(destination) {
   }
 }
 
+function provisioningTemporaryPrefix(target) {
+  return `.firelink-engines-${target}-`;
+}
+
+function provisioningTemporaryOwner(target, candidate) {
+  const suffix = path.basename(candidate).slice(provisioningTemporaryPrefix(target).length);
+  const separator = suffix.indexOf('-');
+  const pid = separator >= 0 ? suffix.slice(0, separator) : suffix;
+  return /^\d+$/.test(pid) ? Number(pid) : null;
+}
+
+/**
+ * Removes only staging directories created by a provisioner whose PID is no
+ * longer alive. Legacy directories without an owner PID remain untouched so
+ * a concurrent or ambiguous provisioner can never lose its staging tree.
+ */
+export async function removeOrphanedProvisioningDirectories(destinationParent, target) {
+  const prefix = provisioningTemporaryPrefix(target);
+  for (const entry of fs.readdirSync(destinationParent, { withFileTypes: true })) {
+    if (!entry.isDirectory() || !entry.name.startsWith(prefix)) continue;
+    const candidate = path.join(destinationParent, entry.name);
+    const owner = provisioningTemporaryOwner(target, candidate);
+    if (owner === null || owner === process.pid || isProcessAlive(owner)) continue;
+    await removePathWithRetry(candidate);
+  }
+}
+
 /**
  * Restores the only previous payload left by a process that died after moving
  * the destination aside but before publishing its replacement. Multiple
diff --git a/scripts/engine-payload-promotion.node-test.js b/scripts/engine-payload-promotion.node-test.js
index 013bc27..a6c3e96 100644
--- a/scripts/engine-payload-promotion.node-test.js
+++ b/scripts/engine-payload-promotion.node-test.js
@@ -6,6 +6,7 @@ import test from 'node:test';
 import {
   promoteDirectory,
   recoverInterruptedPromotion,
+  removeOrphanedProvisioningDirectories,
   removePathWithRetry,
 } from './engine-payload-promotion.js';
 
@@ -126,3 +127,24 @@ test('removes orphaned backups from dead provisioners after a successful publish
     fs.rmSync(root, { recursive: true, force: true });
   }
 });
+
+test('removes only provisioning staging owned by a dead PID', async () => {
+  const root = temporaryDirectory();
+  try {
+    const target = 'x86_64-unknown-linux-gnu';
+    const orphaned = path.join(root, `.firelink-engines-${target}-999999999-dead`);
+    const live = path.join(root, `.firelink-engines-${target}-${process.pid}-live`);
+    const legacy = path.join(root, `.firelink-engines-${target}-legacy`);
+    fs.mkdirSync(orphaned, { recursive: true });
+    fs.mkdirSync(live, { recursive: true });
+    fs.mkdirSync(legacy, { recursive: true });
+
+    await removeOrphanedProvisioningDirectories(root, target);
+
+    assert.equal(fs.existsSync(orphaned), false);
+    assert.equal(fs.existsSync(live), true);
+    assert.equal(fs.existsSync(legacy), true);
+  } finally {
+    fs.rmSync(root, { recursive: true, force: true });
+  }
+});
diff --git a/scripts/provision-engines.js b/scripts/provision-engines.js
index b89d644..fe40272 100644
--- a/scripts/provision-engines.js
+++ b/scripts/provision-engines.js
@@ -1,18 +1,21 @@
 #!/usr/bin/env node
 import fs from 'node:fs';
 import path from 'node:path';
-import { execFileSync } from 'node:child_process';
+import { execFile } from 'node:child_process';
 import { fileURLToPath } from 'node:url';
+import { promisify } from 'node:util';
 import { collectRegularFiles, sha256 } from './engine-payload-integrity.js';
 import { downloadEngineArchive } from './engine-download.js';
 import {
   promoteDirectory,
   recoverInterruptedPromotion,
+  removeOrphanedProvisioningDirectories,
   removePathWithRetry,
 } from './engine-payload-promotion.js';
 
 const __dirname = path.dirname(fileURLToPath(import.meta.url));
 const repoRoot = path.resolve(__dirname, '..');
+const execFileAsync = promisify(execFile);
 const sourceLock = JSON.parse(
   fs.readFileSync(path.join(repoRoot, 'engine-sources.lock.json'), 'utf8')
 );
@@ -37,17 +40,34 @@ if (!targetSources) {
 }
 
 const destination = path.join(repoRoot, 'src-tauri', 'provisioned-engines', target);
-const destinationParent = path.dirname(destination);
-fs.mkdirSync(destinationParent, { recursive: true });
-recoverInterruptedPromotion(destination);
-// Keep staging on the destination filesystem so the final rename is atomic.
-const temporary = fs.mkdtempSync(path.join(destinationParent, `.firelink-engines-${target}-`));
-const payloadDestination = path.join(temporary, 'payload');
-fs.mkdirSync(payloadDestination, { recursive: true });
 const isWindows = target.includes('windows');
 const executableSuffix = isWindows ? '.exe' : '';
+const provisioningAbortController = new AbortController();
+const signalNames = process.platform === 'win32'
+  ? ['SIGINT', 'SIGTERM']
+  : ['SIGINT', 'SIGTERM', 'SIGHUP'];
+const signalHandlers = new Map();
+for (const signalName of signalNames) {
+  const handler = () => {
+    if (!provisioningAbortController.signal.aborted) {
+      provisioningAbortController.abort(new Error(`Engine provisioning interrupted by ${signalName}`));
+    }
+  };
+  signalHandlers.set(signalName, handler);
+  process.on(signalName, handler);
+}
+
+let temporary;
+let payloadDestination;
+
+function throwIfProvisioningAborted() {
+  if (provisioningAbortController.signal.aborted) {
+    throw provisioningAbortController.signal.reason;
+  }
+}
 
 async function download(name, source) {
+  throwIfProvisioningAborted();
   const sourcePath = new URL(source.url).pathname;
   const archive = path.join(
     temporary,
@@ -58,14 +78,23 @@ async function download(name, source) {
     url: source.url,
     archive,
     expectedSha256: source.sha256,
+    signal: provisioningAbortController.signal,
   });
+  throwIfProvisioningAborted();
   const extracted = path.join(temporary, `${name}-extracted`);
   fs.mkdirSync(extracted);
   if (archive.endsWith('.zip') && process.platform !== 'win32') {
-    execFileSync('unzip', ['-q', archive, '-d', extracted], { stdio: 'inherit' });
+    await execFileAsync('unzip', ['-q', archive, '-d', extracted], {
+      stdio: 'inherit',
+      signal: provisioningAbortController.signal,
+    });
   } else {
-    execFileSync('tar', ['-xf', archive, '-C', extracted], { stdio: 'inherit' });
+    await execFileAsync('tar', ['-xf', archive, '-C', extracted], {
+      stdio: 'inherit',
+      signal: provisioningAbortController.signal,
+    });
   }
+  throwIfProvisioningAborted();
   return extracted;
 }
 
@@ -123,6 +152,18 @@ function writePayloadManifest() {
 }
 
 try {
+  const destinationParent = path.dirname(destination);
+  fs.mkdirSync(destinationParent, { recursive: true });
+  recoverInterruptedPromotion(destination);
+  await removeOrphanedProvisioningDirectories(destinationParent, target);
+  throwIfProvisioningAborted();
+  // Keep staging on the destination filesystem so the final rename is atomic.
+  temporary = fs.mkdtempSync(
+    path.join(destinationParent, `.firelink-engines-${target}-${process.pid}-`)
+  );
+  payloadDestination = path.join(temporary, 'payload');
+  fs.mkdirSync(payloadDestination, { recursive: true });
+
   const ytdlp = await download('yt-dlp', targetSources['yt-dlp']);
   copyExecutable(
     findFile(ytdlp, isWindows ? ['yt-dlp.exe'] : ['yt-dlp_linux']),
@@ -143,8 +184,12 @@ try {
   copyExecutable(findFile(aria2, isWindows ? ['aria2c.exe'] : ['aria2c']), 'aria2c');
 
   writePayloadManifest();
+  throwIfProvisioningAborted();
   await promoteDirectory(payloadDestination, destination);
   console.log(`Provisioned locked engine payload at ${destination}`);
 } finally {
-  await removePathWithRetry(temporary);
+  if (temporary) await removePathWithRetry(temporary);
+  for (const [signalName, handler] of signalHandlers) {
+    process.removeListener(signalName, handler);
+  }
 }
diff --git a/scripts/release-workflow.node-test.js b/scripts/release-workflow.node-test.js
new file mode 100644
index 0000000..ed02ef2
--- /dev/null
+++ b/scripts/release-workflow.node-test.js
@@ -0,0 +1,17 @@
+import assert from 'node:assert/strict';
+import fs from 'node:fs';
+import path from 'node:path';
+import { test } from 'node:test';
+
+const repositoryRoot = path.resolve(import.meta.dirname, '..');
+const releaseWorkflow = fs.readFileSync(
+  path.join(repositoryRoot, '.github', 'workflows', 'release.yml'),
+  'utf8',
+);
+
+test('release Linux dependency installation is mirror-normalized and bounded', () => {
+  assert.match(releaseWorkflow, /azure\\\.archive\\\.ubuntu\\\.com/);
+  assert.equal((releaseWorkflow.match(/Acquire::Retries=3/g) || []).length, 2);
+  assert.equal((releaseWorkflow.match(/timeout --foreground --signal=TERM --kill-after=30s 10m apt-get/g) || []).length, 2);
+  assert.doesNotMatch(releaseWorkflow, /^\s*sudo apt-get (update|install)/m);
+});